TPS3850-Q1: Equation (6)

Shinji Tsuji

Genius 14119 points

Part Number: TPS3850-Q1

Hi team,

In datasheet table 8-4, there is a note as below.

(1) Minimum and maximum values are calculated using ideal capacitors.

Could you advise how to calculate the MIN/MAX tWDU value with capacitor tolerance takes into account?

regards,

over 3 years ago

+1 Jesse Villanueva over 3 years ago

TI__Mastermind 18710 points

Hi Shinji,

Thank you for your question. The process is outlined below.

Twdu(typ) = 77.4 * Ccwd * (+/-cap tolerance) + 0.055

Then when you get the boundary range for the timing, you can use that value to calculate the other boundaries of the window.

Jesse

0 Shinji Tsuji over 3 years ago in reply to Jesse Villanueva

TI__Genius 14119 points

Hi Jesse-san,

In the datasheet Figure 8-4 shows the minimum and maximum tolerance calculated based on ideal capacitor, so the min and max tolerance in this figure

shows the tolerance of the device itself.

If I calculate capacitor tolerance using the equation above, how can I add the device tolerance?

regards,

+1 Jesse Villanueva over 3 years ago in reply to Shinji Tsuji

TI__Mastermind 18710 points

Hi Shinji,

The Twdu(typ) you get from the equation get multiplied to a constant based on your SET0 and SET1 configuration.

For example: Twdu(typ) = 400ms while SET0=1 and SET1=1

so you have Twdu(typ)=400ms Twdu(min)=400ms*.905 Twdu(max)=400ms*1.095 ====>> Twdl(typ) = Twdu(typ)*.5 ==> Twdl(typ) = 400ms*.5 similarly ==>>Twdl(min)=Twdu(min)*.5 Twdl(max)=Twdu(max)*.5

You just have to repeat the process for your worst case values.

I hope this helps.

Jesse

0 Shinji Tsuji over 3 years ago in reply to Jesse Villanueva

TI__Genius 14119 points

Hi Hesse,

Thank you!

regards,

Power management

Power management forum

TPS3850-Q1: Equation (6)